PSI - Go by Manual or what's on tire?

Discussion in 'Lawn Mowing' started by hillndale, Jun 1, 2005.

  1. hillndale

    hillndale LawnSite Member
    from Maine
    Messages: 214

    I assume you go by the Manual, but thought I'd ask -- I have a new Scag Z Cat and thought I better check the tire pressure since reading how much tire pressure effects cut and handling. Well they are set closer to what's on the tires. The manual says 12PSI in drive wheels and 25PSI in castors. On the tires it says: drive tires 24PSI max and castors say 46PSI max. So the manual is calling for roughly half what the tire manufacturer is saying. Could someone please enlighten me. Many Thanks

  2. Grass Masters

    Grass Masters LawnSite Member
    from NC
    Messages: 85

    GO by what is on the tire because the maunal was written for the tires taht was placed on any unit at the factory.

    The tires you buy may or may not meet the same standards as the ones that were at the factory..

    What does it say about min.
  3. hillndale

    hillndale LawnSite Member
    from Maine
    Messages: 214

    It doesn't mention minimum. The tires on the machine came with the machine. Are you saying the manual isn't model specific?
  4. LightningLawns

    LightningLawns LawnSite Senior Member
    Messages: 279

    max psi is just the maximum that the manufacturer of the tire recommends you can put as little as you want just don't exceed the max. Go with what the manual says otherwise your cut height might be off.
  5. riches139

    riches139 LawnSite Senior Member
    Messages: 369

    The high pressure on the tire is to seat it to the rim during the manufacturing process.

    They usually come overinflated unless the dealer did his job and adjusted them.

    You'll find that 24# in rear and 46# in front will make it ride like a rock. :angry:
  6. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I always go by what's on the tire, too.

    Far as cut-height, not only should this be influenced little to none, but I check this from time to time, in my case when the WB sits on a level surface, the blades are 4 fingers from the ground. Since both my Wb's are the same model and make, both are set to the same height - So if one should actually break down in the middle of a yard, I can come back with the other and finish it without any problems.

    50 psi is what I have in the front, 30 in the rear (for my fixdeck WB). That way when I hit a bump, low tire air-pressure doesn't act like a shock absorber, causing the deck to 'sink' towards the turf and creating a nasty scalp. That, and it rules when curb-jumping.
  7. Oldtimer

    Oldtimer LawnSite Bronze Member
    Messages: 1,459

    Over inflate mower tires and they could be ruined. They are not belted and will stretch.

  8. hillndale

    hillndale LawnSite Member
    from Maine
    Messages: 214

    Interesting and thanks -- I'm 2 for 2 -- some say follow manual and others go by what's on the tires. The drive wheels on my machine even have little stickers that say 12PSI. I'm currently at twice that.

    It has just started drying out here, but my tires have been spinning a lot. I know lowering the pressure will lessen the bumpiness of the ride & I would think definatelt effect cutting heights. How does pressure effect impact on turf?

  9. Precision

    Precision LawnSite Silver Member
    Messages: 2,995

    less tire pressure gives more grip

    More tire pressure gives more height and more speed

    Tire pressure should be run on the softer side to create less wear on the turf, less damage to the machine/driver and to create a larger contact patch.

    If the manual says 12psi try it there and see how she runs. Different types of tires require different amounts of pressure. The bald from the factory castors with really thick walls typically require much less than thin treaded tires to maintain shape.

    Unless you own a Ferris you tires are the only shock absorber you have.
  10. hillndale

    hillndale LawnSite Member
    from Maine
    Messages: 214

    Thanks very much Precision -- I noticed I've been spinning my wheels (so to speak) a lot, even backing up trailer ramp. I thought something was wrong. Though you say softer tires create less wear, I would think the opposite, but I totally trust your expertise & will set the tires to the "manual specs" & see what the response is. Thanks again


Share This Page